Non-expansion Hiding Secret Image in Visual Secret Sharing with Shift Style

The paper presents a visual secret sharing scheme, which not only shares an image of moderate confidentiality between two noisy transparencies, but also hides in these two transparencies another secret image. None of the transparencies alone can reveal anything about the image. Later, people can view the image by simply stacking the two transparencies; on the other hand, after change the stack location the other secret image can also be extracted. Different from traditional VC with shift style, the method have no size expansion and can recover original lossless with computation fast. The method also solves the difficult to align two transparencies.